Discount clubs: Pay to shop?

With Amazon Prime raising its annual membership from $79 to $99, many are rethinking membership in discount clubs that charge a fee.

Consumer experts say they only make sense if you're using them routinely and creatively, like buying gas from your warehouse club.

"Those prices can be substantially cheaper than what you're going to find elsewhere. If there's one on your way home, the savings on gas could easily pay for that membership and very, very quickly," says CNBC consumer reporter Kelli Grant.

Grant recently researched the value of membership in discount clubs and concluded you have to comparison shop.

"For all of these, it's looking at how much value are you going to get out of the membership instead of paying a la carte," she says.

Grant also says frequent users of Amazon.com may still find value paying for Amazon Prime because of what all they get through the Kindle lending library, streaming video service and free shipping.

Another issue to consider: A study by Consumer Intelligence Research Partners found people with memberships often spend more to justify their membership fee.